The objective of this project is to delineate the mechanisms of opiate involvement in parasitized animals and to understand the relationship between this opiate activation and behavioral abnormalities. White mice infected with the intestinal tract helminths Heliogomosomoides polygyrus, Hymenolepis diminuta, and Ascaris suum will be examined in regard to opioid induced analgesia changes in activity levels, anxiety levels in a plus maze, and spatial learning. The effects of a variety of opioid antagonists as well as the interactions of morphine and parasitic infection on behavioral alterations and immune response in mice will be explored. The presence and secretion of neuropeptides including dynorphins and enkephlins as well as morphine will be examined in these parasites by HPLC and radioimmune assay. The effects of morphine and anandamide on the ganglia of Ascaris suum will also be examined. Based on these studies, it is our expectation, that the basis of opioid behavioral alterations will be determined and establish a role for these signaling molecules in behavior that transcends analgesia, thus having important consequences for psychiatry.